There are methods for forming color images by using photo-polymers or diazo compounds, called the overlay method and the surprint method, which are conventionally known as the methods for making color proofs from plural black-and-white halftone images prepared by subjecting originals to color separation and halftone image conversion treatments in the color graphic arts/printing process.
The overlay method is very simple, inexpensive for proof preparation, and advantageous in that all what has to be done for color proof reading is superpose film sheets for four different colors (subtractive three primary colors plus black), but has the disadvantage that the superposition of the film sheets brings about gloss, thus leading to providing an image quality different from that of the resulting print.
The surprint method is to superpose colored images on a support, and as the method there are those for forming a colored image by toner development, utilizing the adhesion property of a photopolymerizable material, as described in U.S. Pat. Nos. 3,582,327, 3,607,264 and 3,620,726.
Japanese Patent Examined Publication (hereinafter abbreviated to JP E.P.) No. 27441/1972 and Japanese Patent Open to Public Inspection (hereinafter abbreviated to JP O.P.I.) No. 501217/1981 describe another color proof making method in which a light-sensitive colored sheet is used to have its layer transferred onto a support, exposed and developed to form an image, then on the formed image layer is provided another light sensitive colored sheet's layer to be subjected to similar process, and then repeating similar procedures, whereby a color proof is prepared.
JP O.P.I. No. 97140/1984 describes a method in which a colored light-sensitive sheet is exposed through a corresponding color-separation image film and developed to thereby form a colored image to be transferred onto a support, which is followed by forming and transferring onto the colored image in sequence different other colored images in the same manner, whereby a complete color image is formed on the support. For the toners and coloring agents for use in the formation of the above color image there may be used similar coloring materials to those for making printing inks, so that the resulting colors of the obtained color proof prepared by using them near those of actual prints.
The above-mentioned methods, however, require much labor for superposing and transferring images onto a support in the color proof making process, so that they have the disadvantage that they take time and are costly.
For solution to the above problems JP O.P.I. Nos. 113139/1981, 104335/1981, 280746/1987, 280747/1987, 280748/1987, 280749/1987, 280750/1987 and 280849/1987 disclose methods for making color proofs by use of a silver halide color photographic light-sensitive material having a white support.
The method disclosed in the above publications is such that a plural number of color-separated black-and-white halftone dot images obtained by the color separation/halftone image conversion of a colored original are printed in sequence in the contact printing manner onto a single sheet of color photographic paper, which is then subjected to color development to thereby form a color image composed of dyes produced from the couplers; the thus formed color image is used as a color proof.
However, this technique has the following shortcomings. When a color proof is prepared so that a color image is brought close to that of original print, the density of black images such as characters is insufficient compared to that of the original print, and when a color proof is prepared so that the black image density is enhanced to be close to that of the original print, closeness to the original print of the color image deteriorates. Therefore, it is difficult to obtain a color proof satisfying both image criteria.
In order to overcome the above shortcomings, a light sensitive material is disclosed in JP O.P.I. No. 2-212835/1990 which comprises a yellow layer, a magenta layer and a cyan layer, each layer having a spectral sensitivity wavelength region different from each other and a common spectral sensitivity wavelength region. As is apparent from the description, the density of the emulsion having common sensitivity wavelength can not attain a black image density and even if Y, M, C densities are added, only a density of about 0.3 is added. Therefore, in order to obtain the sufficient density, when exposure is carried out through a yellow image original, through a magenta image original, and through a cyan image original in close contact with light sensitive material, exposure-is carried out through a black dot image original together with the yellow, magenta or cyan dot image original. As a result, reproducibility of either a small black image dot or a small monochromatic image dot deteriorates which is obtained by exposing through a black image or monochromatic image original being farthest from the light sensitive layer. A technique is disclosed in JP O.P.I. No. 61-233732/1986 which comprises, in addition to a yellow color layer, a magenta color layer and a cyan color layer, a fourth black layer having a maximum spectral sensitivity wavelength different from the other layers. This technique has the disadvantages that the four layer coating is a complex production process, the emulsion thickness increases, resulting in deterioration of image sharpness, and further, exact reproduction of image information is difficult. A technique is disclosed in JP O.P.I. No. 5-134350/1993, which reproduces, both black image and color image by a yellow color layer, a magenta color layer and a cyan color layer. The technique requires exposing to light through both black image original and color image original in close contact with the light sensitive material, and the close contact with any of the originals is insufficient, resulting in deterioration of small-dot reproduction in a black or color image. Further, black image portions are not distinguished from image portions consisting of a combined three color images, that is, yellow, magenta and cyan color images, and there is practically a problem in exact reproduction of shadow image portions.